Means for indicating frequency changes



Jan. 6, 1931. H. SCHUCHMANN 1,787,997

MEANS FOR INDICATING' FREQUENCY CHANGES Filed Oct. 20. 1927 INVENTOR firms scuucumnmv TORNEY Patented-Jan. 6, 1931 UNITE ST .wmml-seal mmi mi Lia-veer ,sinMnns & iiA sKE, AKTIENGESELLSCI-IAFT,"F v GERMANY, A'conronA'rioN or GER ANY j SIEMENSSTADT, NEAR BERLIN;

MEANS FOR INDIcaTiNG FEEQUENCY'CHANGES Application filed. October 20, 1927,.S'erial No. 227,542, and inGerniany A ugust 4 1926. V

Applicationfor this invention filed in Germany, August l, 1926. f

, The object ofthepresent nvention is to construct a device adapted to occasion oppo site mechanical or electrical eiiects, or, more particularly speaking, to insure an adjust ment whenever the frequency of an alternating current goes beyond or falls below acertain normal value.

Other objects of the in vention will appear in the following specification when read in connection with the 7 drawing in which Figure 1 illustrates diagrammatically a. basic arrangement of the fundamental fca-j 7 tures of the invent on; I

FiguresQ and 3 illustrate diagrammatically in vector form conditions existing in the different circuits; I I v j Figure 4 illustrates one practical "circiiut incorporatii'igthe invention Figure 5 diagrammatically shows another embodiment of the invention in which the adjustability of the phase angle is attained byrotor coils and q igure 6 diagrammatically shows the potential conditions eXisting in the circuit of Figure 5.

Means involving the use of electron dis-' charge (lGVlCES are known to the art utilizing.

the shift in phase'in the case of frequency inequality between two circuits in such a way that either the alternating current potential subject to controlserves as the plate-poten-,

tial, whilethe potential derived from anoscillation circuit is impressedupon the grid ot an electron tube, or else bothof the said potentials before referred to are supplied to the grid.

Now, in accordance withthe disclosures of the present,inventionthe phase angle of'the grid potentialis made adjustable at different values so that, in the presence of phase equality, or co-phasal condition, there results Zero potential, while in case of phase dissimilarity, it changes uniformly in both direc tions from said zero value.

Adjustment of the phase angle is insured by inserting,zin the circuit influencing the grid oftlie electron tube Whose potential is dependentupon the standard oscillation circuit and an alternatingcurrent potential acting-1 thereon, an adrentsource W in the circuit I of which there is aself-inductance coil L a condenser C and Across the. latter an' ohmic resistance R is connectedthe standard oscillation circuit II'containingacapacity C aself-inductance.

coil L ianda resistance R Since the series connection of the condenser C and-the self inductance coil L constitutes a purely ohmic resistance, lt wlll be seen that series resonance arises inthe presence of resonance, and the. currents flowingincir-cuits I and II are in :phase. Ifthe resistance coupling is properly chosen, it ispossible-to make conditions so thatthe potential at the self-inductance coil L of circuit I, in absolute value,-is equal and opposite to the. potential at the condenserv J of circuitII, as'can beseenfrom Fig. 2. The total potential between points a and b in a circuit diagramas shown inFi-g. 1, therefore, in the. presence of perfect tuning, is equal to zero, while in caseof untuning J1 and J it increases very rapidly by the" angle pin one direction or the other of the resonance point by way of resistance Ris the circuit II which may serve as the measuring standard circuit.

The latter comprises avariable condenser C and the primary winding 6 of an air-core transformer, T Theseconda-ry windings t and of the transformer T and T re;

spectively, are connected in oppositiolnthe resultant potential being-fed to the grid. g of an amplifier tube V This potential is fur"- ther supplied by way of the transformer T whose primary is connected in the plate circuit of the amplifier tube V through its secondary winding t to the grid 9 of rectifier tube V A battery B serves to supply a grid biasing potential. The plate circuit contains a battery B while the plate circuitof the second tube V contains a measuring instrument at. i

as soon as an alternating potential reaches the grid 9 of the first tube, hence indicating thereby the fact that the. frequency to be test has deviated from the normal frequency.

For-the purpose of increasing the indicating. sensitivity the'measurmg apparatus 03 may be compensated by means of connecting in a counter voltage so that it will indicate zero in the position of normal frequency.

In the presence of frequency equality, the series combination comprising the condenser C2 and the coil t 'of the circuit II presents a purely ohmic resistance. Thecurrentsflowing in circuitsI'and II, owing toresistance coupling, are in phase, and also the potentials in' the unloaded secondary windings :6 and t; of transformers T and T The ntegral potentialof the oppositely connected winding's 6 and ti, if-the coupling of the two circuits I'and- II is properly chosen, is equal to zero, and the ineas'uringdevice (Z remainsuna affected. However, upon the arising of the slightest departure in the frequency to be measured, or by slight; setting of the condenser C the phase of'tlie currents in circuits I and II undergo an alteration and so do the phase relations dependingthereon of the secondary'potentials in the windings t and t of the transformer T and- T, The integral potential differs from zero, and the measuring device d shows a response.)

-In the case of tonal frequencies the measuring device may consist of a single amplifier tube. Iii-the case of radial frequency, io'wever, it is necessary to measure tli current in the plate circuit and, undereertain conditions, a rectifier tube 'acting'as an amplifier may be required. As to the rest, instead of using a variable condenser, also the coil 2?,

or coil't may be made variable.

The energy consumption of the arrangement is very small, and the responsiveness or sensitivity very high, since on account of the 7 connection in opposition, the two secondary potentials may be chosen very great so that the difference assumes considerable values even in the presence of the slightest alterations in the phase angle. By variation and re-adjustment of the condenser C not only exact adjustment, but also an absolute measurement of speed and the like is possible by noting the time ittakes the current in-one' I branch to attain the same conditions as those of the other.

*device, is adjustable in a particularly convenient manner, is shown. by the circuit arrangement according to' Figure 5. -The illustration shows at the same time a symmetrical arrangement which renders vthe'indications of c f the measuring apparatus to'a great extent in- The measuring device Z,connected the anode circuit of the rectifier tube V responds placed, when using this circuit arrangement, I

by a relay for the readjustment to the correct frequency.

In the circuit I are disposed the alternating current source V], the coils L and L; ofthe rotating field varionieters, a condenser- C connected in series with an ohmic resistance R, as well as the windin of a transformer T, which insures the coupiing with the normal oscillating circuit II. There may, of course, be used in place of the transformer T also a resistance coupling according to Figures 1 or 1 l. In shunt with the coils L and L and the series connections'of C and R are further disposed coils of the rotating field varionieters L and I as well as a choke 0011 D V The resistance valuesof the variometer coils, also of the condenser G the ohmic resistance R- and the choke D.- are selected in the manner that the currents which flow, on the one hand,

through the coils L and L 'and, on the other hand, through L and L are shifted in their phase by about 90. By means of the crosslike arrangement of'tlie coils'of the rotating field variometer there are produced two opposing rotating fields of, as nearly as possi- 7 ble, equal amplitude. I In the rotating fields are adjustably arranged further coils D and D which are suitably mounted on a common axis. The two variometer coils D and D I are suitably connected, on the one hand, with the grids g 9. of the rectifying or amplifying tubes V and V and, onthe other, are joined together to'the winding t of a transformer T which is disposed in the normal oscillating circuit II. The voltage of the open circuit for the grids g and of the above mentioned tubes is supplied by battery B which is connected, on the one hand, with the cathodes of tlie'tubes and, on the other hand, with the transformer winding i In the plate circuit of the opposing tubes V and V is disposed the plate battery B and a differential apparatus or differential relay d.

winding 25 and whichgis always common to the two grid potentials. .7 To this potential are. vectorially added the potentials e Ore which are furnished by ltherotors D and D respectively. In the normal state these two potentials must be of exact equal length and must be disposed synnnetrically to the com mon potential o They are, besides, in their absolute length approximately equal to this common potential 6F and shifted with respect to thelatter by-the phase angle a, Theangle a is chosen as large as possible, however, it must not reach 180. A suitable value would be around 170. This phase angle may be adjusted at will by means of the rotation of the rotors D and D which are coupled with one another but which are also individually adjustable. With a correct balancing of the elements of the circuit arrangement and of the operating voltages of the tubes the grid potentials e and e are of equal value in the normalgstate with the result that the indicating device cl, disposed in the plate circuit, shows zero. With the slightest deviation of the frequency to betested from the normal frequency the phase of the current in the normal oscillating circuit 11 changes, hence, the vector e rotates, its end point moving thereby approximately in. a circle. When, forinstance, the vector 61.1 in Figure 6 turns to the left, the grid potential e increases and the grid potential c decreases. In this condition the change of the potentials e; and o is negligible in its siz-ewith respect to the change of e with the result that for the change of the grid potentials the change of the potentials 6]; is essentially the influencing factor. This change is also in this arrangement again quite considerable due to the almost straightposi- 7 tion of the two part potentials 6F and 6 or 6 and e so that the entire arrangement responds with great reliability to even extremely small dissonances. s

The rotating field variometers represented in Figure 5 arethe means for insuring a particularly convenient and exact adjustment of the part potentials to be tapped, it is, however, directly possible to tap the component potentials in different manner from the cir cuit to be tested or the standard circuit, for instance by meansof transformers according to Figure 4. What has to be done in this case is simply to take care that each two component potentials, which are combined to a resulting grid potential, have a phase shift .of not quite 180, for instance about 17 0, with respect to one another and that they are of about equal absolutelength. U

Having thus described my invention what I desire to protect by Letters Patent is as follows:

1. A device for indicating changes in the frequency of a generator which comprises a generator circuit having an inductance and a capacity therein, an oscillation circuit coupledgthereto and electron tube circuit arrangement having an input "circuit and an outputcircuit means comprising said generator circuit and said oscillation circuit for supplying energy to said input circuit and me in said output circuit affected by changes in I I the supplied input energy.

2. In a device for indicating changes frequency of a generator, a generator circuit comprising a capacity and an inductance, an oscillationcircuit coupledto said generator circuit and having tuning means therein, an electron tube circuit arrangement having output and inputcircuits current responsive means in said output circuit, means for cou pling each of said two mentioned circuits to-said inputcircuit whereby upon any changes occurring in the frequency of enerin either first two mentioned circuits the energy in the output circuit of said electron tube circuit arrangement will be affected and means controlled-thereby for effecting said current responsive means.

8.'In a device for indicating changes in the frequency of an oscillating circuit, a standard oscillation circuit coupled thereto, differential phase responsive means coupled to each of Cll'ClllLS and means controlled thereby for detecting any changes occurring in saidos llation circuits.

l. Tnfasystem for indicatin frequency changes, an oscillation source, a circuit comprising a reactance, a resistance and coupling means in oscillation circuit coupled to said first named circuit, an electron discharge tube circuit arrangement having input and output circuits input circuit being. coupled by means 5. In a device for indicating changes in the frequency of electrical oscillations, a pair of rotating field variometers each thereof having two fixed windings and a movable winding, said windings being arranged so that the rotating field in one of said variometers is opposed to the rotating field of the other, a closed circuit including a source of electrical oscillations, one corresponding fixed winding for each of said variometers, a capacity and a resistance all in series with a coupling coil, acircuit comprising the other of said fixed windings of each ofsaid variometers and a reactance shunted across said first two windings said capacity and said resistance, a pair of triode circuits the control elect-rode of one thereof being connected to one end of one of said movable windings and the in the control electrode of the other tiiode being connected to one end of said obher movable. win-fling, means for cennecting the free ends of saidrmovable windings and means comprising a second coupling coil and a current source fer cennecting said lee-unarmed means to the filame of each of said riefles e tun d oscillaeory circuit includin la capacity andfiwo coils 111 in series one )I'sail coils being 0011- ..K pled to said first mentioned coupling-coil, the ether thereof being; coupled to said second coupling coil and me 5 including a current responsive device for connecting the output circuitsrof sai'ltriodes in opposirion. V V HANS, SCHUCHMANN. 

